Signaling arrangement for two-wire telephone lines



May 27, 1952 H. GARDl-:RE 2,598,159

SIGNALING RRANGEMENT FOR TWO-WIRE TELEPHONE LINES I 3 l/VE 10-1 L l IT 9 L//VE H. GARDERE May 27, 1952 SIGNALING ARRANGEMENT FOR Two-WIRE TELEPHONE LINES Filed oct. 22, 1948 3 Sheets-Sheet 2 /lvvE/vra/e HENRI GARDE/QE arr-nerven? May 27, 1952 #s sheets-sheer 5 Filed Oct. 22. 1948 irl-afNew- Patented May 27, 1952 A.uN-1 TED vsiiritzs PATE-NYT i lsiiGNALING ARRANGEMENTYFOR TWO-'Winn TELEPHONE LINES Henri rGraridere, "Ifarisv, France,v assignor izoifCqni-` pagnie- Industrielle des Telephnes, Parisi, 'Fi'ance,a corporation of France 'Apliiioationotoboi122, 194s! Vseriali No.1 55993 In France October -28, 1947 Vl' :My invention relates to a low 'frequency"" siga nal'linigarrangement, allowing, in Y'a"tele'p'hbne System using av two-'wire `transmission "1ine, "the r 'itransmiss'ion'ofringing'or signallin'g'or dialing lcurrents in Yo'rde'r'that these'signal'ling currents "slialljbypass a talking' currentA rep eat'efconneoted in'the two-Wire line;

"Low-frequency signalling arrangements 'as heretofore known' have "generally comprised' 'two lays-assigned to Vone dirootion 'of transmission, is

oomected'so as to open,*whenthat'rolayiseiierf gizedj, the 'errer'gijzation circuit' ortho Y'rerays 'of fthe 'Iiriiiyoo-poiioiiig animation, ser. No. 311034; iiiodiiiiiiofi, 1948,nowpaioni No. 2,594,007; .is-

of'sigriais 'by Two WiroTelephone Lines; I naif@ 'signalling arr'ahaits In"other' known arrangements, the 'first irliay offea'oh of these setsis replac'edby ayaiiiini trio-ole.

However, in none oftl'iese devicesof' the prior `art are the :active meinloers'constitutdsolely by yacuufii' tubes, so` Vthat 'tlieirni'anner of 'operation the signals;A

'Trie-signallingarrainigenioritto which ihi'sipos;

'ent' vintentionrelates,"employs as active inen'i'bei-s, 'vacuumiamplinr'tubes Awith-one orfiri'o'r grids, n with thaexclusioii ofan'y mechanical' 'device and anyV` device causing feedback. 'transmission of the signals V`in both directions 'along ta" 'two-wire line; `Without "initiating 'any' os- Aoina'tioiis orringiiigr' howlingtoiies.'

`It jensres' the s infine oasoinwriioh 'the amplification i'iecsfsfoliiii's-a (015179-416) ,.2 sary'fo'r theretrans'rnissinof the signals or ring ing"tn1're'-nt,4 is not todgreatfthe sinalling "ar-v rangement 'accordingl Vto 4'this present invention nay' comprise as actiyeinernbers only Atwnftfubs; onef'or each direction offtrans'niil'ssiomeach )'glavy-` ing the'part of a set ofrela'ysof the-usual signal-'- ling' devices of the 4prior arti Itis even-possible to use as active devices "of" the signallingiarrangea nient,jtl'1'ev tubes *of thi:l ltalking current repeater itself A'to which itis aftiaoiiedfin suoirmaiijiiw that the signalling device-:may Lbe carried into eiect 'bythe addition vto therepeater bf purely passive "devifes l y f Y The' signalling'arrangementinconformity With this p'r'esent 'invention 'is "characterized "in thatit comprises.; foreach direction of transmission, the following"dei/ities:v y

(1*) An"a'mp1lfier With 'one 'or 'more' Vacuum tubes" `('ac'ordin'g tothe necessaryianiplications) toys/hose input i's'applied aniincident'si'gnal to be reetransinitted. p Kx s (2) `A"1Ovc1k1fig fde'vC'e energized by' v.the incident Vsignal;j'andvcancellin'g out "the'ain ofthe ampli'- er of '^th"e otherjvdi'rectionas' ,soon as the ampli- 'tudeot the incident signalattains a predeterminedyal'ue.' K l 3) A jiiniiriai valu'jireot 'device :placed below the lockingA device and attenuating orsuppressing the effect of the signal at the input of the 'ainplier '-injthe' other direction as long'as thelockin g of 'the'sanie is not sufficient. y

. 'rho 'accompanying drawings repli-es'ont 'by way of example, vvariousetnbodinient's of the signalling arrangement according 'to this present invention.

' Figs. 1, 2, Blandiar'e block diagrams showing'th'e respective 'positins'of the 'various' devices inthe circuit. ."5 is amore detailed diagram ofthe circuit ofjlig'. '1,"and1Fi`g, @represents an eibodi'- linent "of the signalling Varrangelnent v:em'plf'iying the v'same tubes asthe talking'our'rent' repeater with which it is associated.

1n-Fig.j1,Skandia are ineoteriiiiiiais of 4the two-Wire line 'between which th signalling arrangement n'onnec'tei;y The `talking"ci'irren peater,`which'i`s in addition to thesignallitig arrangement, and is: notshown is likewise 'connecte edheinveen vthese points I designatesthe vac'- ull'n ltube all/'lpli' Which 'ampis lthe"'SLiglllS 'in theidirectionjof lo toward's'a Tothoutp't terminals 'l of lthis amplifier 'isciected' `'t'l'ie device s *which* brings about the iockingof'the ampiiiier ii diiooidir'i other 'direc-tion." 'Beother direction of transmission, and comprises the amplifier 2, the locking device 4 connected at 8, and the unit with the liminal value effect 6.

The locking devices 3 and 4, the task of which is to lock respectively the amplifiers 2 and I, may be constituted in any known manner. It will be advantageously constituted by a bridge of dry rectifiers giving a negative polarization voltage on a control grid of a tube of the amplifiers.

The liminal value devices may likewise be constituted in any desired manner. An advantageous embodiment is obtained by means of a polarized network of dry rectifiers.

The manner of operation of the arrangement of Fig. 1 is as follows:

When a signal appears at III it is amplified by amplifier I and the locking system 3 tends to prevent the return of the current going in the other direction through the amplier 2. But it is clear that if, as from the shunt 'I the amplified signals should be transmitted directly towards the terminals 9 of the line and then fed back to terminals I0, then oscillation would start. In fact, the so transmitted current would always have, at a given instant, a rather weak amplitude in order that the effect of locking due to device 3 be negligible, so that this returned current would be amplified in amplifier 2, then again in amplifier I and so forth; therefore there would be an initiation of oscillations the ampltude of which would moreover, be limited by the locking effect of device 3 and of device 4.

The liminal value effect arrangement avoids this undesired manner of operation by preventing the signal delivered from the output of amplifier I from reaching the input of the other amplifier 2 as long as the locking effect of device 3 is not produced. As soon as the liminal value of the liminal unit 5 is exceeded by the signals delivered by amplifier I, the signals are transmitted tc line terminal 9, but the effect of the locking of device 3 is then sufficient to prevent any amplification of the signa-1 by amplifier 2. I have found that it is possible to regulate the locking effect and the liminal value effect of the respective devices in such manner that the amplitude of the liminal value may be as low as desired so that the amplication ofthe signals may be practically linear.

The order in which the amplifier I, the shunt I and the liminal value device 5 are connected, may be changed, provided that the shunt 'I remains ahead of liminal value device 5; it will be appreciated that the same applies for the devices of the other direction of transmission. Figs. 2 and 3 represent two such modifications ofthe circuit of Fig. l. Moreover the shunt, the locking device and the liminal value device corresponding to one given direction of transmission, may be arranged in the circuits of the amplifier used in that direction.

Fig. 4 shows another modification wherein the liminal value unit 5 is arranged between the line terminals 9 and the amplifier 2, the liminal value device E being then placed between the line terminals I0 and the amplifier I. In such an arrangement as shown in Fig. 4, the amplifier and the liminal value arrangement may be condensed to form one single unit, the liminal value effect being obtained by negative polarization of the grids of the tubes of the .amplifier of value sufcient to cancel out their plate current. Thus the transmission is blocked until the amplitude of the applied signals is sufiicient to cause the plate current of the amplifier tube to appear.

4 This arrangement is particularly economical, but it destroys the linearity of the amplification, unless push-pull tubes be used.

Fig. 5 is a more detailed circuit givenby way of example, of a circuit according to the signalling arrangement according to Fig. l. In this Figure 5, II and I2 designates the tubes of the amplifiers I and 2 (triodes are shown in the diagram but it will be appreciated that it is possible to use other tubes such as tetrodes. pentodes and so forth). The heating circuit of these tubes has not been shown. The plates are energized with a voltage Vp, and the plate current corresponding to the normal rating is obtained when the grids are brought, in relation to the cathodes, to a determined voltage Vg. The locking devices 3 and 4 are arranged in series in the plate circuits of the amplifier tubes II and I2. The locking of the amplifier 2 by the delivered signals amplified by amplifier I is effected in the following manner:

The incoming signalling current from linev terminals ID after amplification by the tube II passes through the transformer I'I to locking device 3 and is rectified by the bridge of rectifiers I3, and the rectified current produces across the terminals of the resistance 31 in the grid circuit of the tube I2 a negative direct bias voltage which is smoothed out by the condenser I9. This bias voltage reduces or cancels out the plate current of the tube I2 thus opposing the transmission through the amplifier 2. In the same manner the amplifier I is locked by the current delivering from amplifier 2, passing through the transformer I8 and the rectifier bridge I4 and applying a negative voltage at the terminals of the resistance 38.

The liminal value devices 5 and 6 which are constituted by the network-s of dry rectiers I5-25 and Iii-2B, function in the following manner which will be described for the direction III-9. the manner of operation in the opposite direction S-IO being analogous:

Two rectifiers I5 connected in series and in opposed direction, are arranged in shunt across the output circuit of the amplifier tube II, they are polarized symmetrically by the plate voltage Vp through the resistance 23, the two halves of the secondary of the transformer 2l, and earth. As long as the current induced in the secondary of transformer 2l by the anode current of the tube II does not exceed the polarization current of the rectifiers I5 the latter behave like a shortcircuit; on the contrary, when the anode current delivered from the tube exceeds the polarization current they behave like a high resistance. Thus the secondary circuit of transformer 2I is shortcircuited as long as the signalling current is lower than the determined polarization current.

This liminal effect is increased by the action of the auxiliary rectifiers 25. These are arranged in two groups constituted each by two rectiers arranged in opposite direction and connected in parallel, each group being placed in series in one of the Wires of the output circuit of the amplifier. Now, it is known that two rectiers connected in parallel and in opposite direction behave like 'a high resistance for voltages lower than a certain limit characteristic of the rectiers, and likel a low resistance or one which is even negligible, for voltages higher than this limit. Therefore the rectiers may be selected in such manner that when the signal voltage amplitudes are lower than the liminal value desired. the rectifiers I5 behave like a short-circuit and the rectiers 25 like a @scarsa cut-out; or open; cir.cuit;. When the liminal valuez ist exceeded short circuitY lid and the cut-out: disappear' and; the: amplified; signals: delivered; tube U pass. freelyftowa'rds line terminal. 9i. Moreover., the. cut-out. eiect of the rectiiiers; 2.5L for-flow.r voltages has the resultof: preventing the effect. of short-circuit. of the. rectiiers: l5 upon. the. currents. coming: from. line. terminal: 9i' for the` transmission directionl -HL The: liminakvalue. system. for tliislatter direc--4 tioniofi transmission from terminal 9l to termi-nal 110:' is; identical; with the liminal system... 5land comprises,therectifiers-` L5 andlZE, the transforme-rwith; nridepointZZ and the resistance 24@ `Eig.. d. represents. an example. ofi the signalling arrangement according to this` presentinvention, associatedwith a talking current repeater andenmloying; the.l same tubes as this repeater` employsi Theipreviously described devicescarry the same reierencenumerals as in the preceding Figures.l:-5.. Only the characteristicslof connection otthetalkingcurrent repeater and of thesignallingarrangementare hereinafter described.

Aitheline' terminals l0 are connected in paral-A lel theinputszofthev talking current repeater land oi' the signalling arrangement for the direction llt-3. Thebl'ockingcondensers ofthe oliierentialI system, 28T of. therepeater have a large-impedancefor thealowfrequency signalling currents sothat the latter areA without action on the repeatercircuitsf. for. talking currents. At the input of the signalling arrangement isY placed` in series, an inductance 301 the impedance of which is high for the. telephone talking currents and negligible forthe low-frequency signalling currents, so that' the-*shunt ofthe signalling device is without eiect' onfv the telephone talkingfcurrentsf. The telephone talking voltage and the' signalling voltage areapplied inseries` in the grid circuit of the tube H through the circuits 35'` and 33. These two voltages cannot interferel by reason of the infinite4 impedanceof the grid circuit. In the output plate circuit of the tube ll the circuits of theV tainingl current repeater and of the signalling current arrangement. are likewise in series. Caref-ulltering prevents them from iniiuencing each other. This filtering is due to theA low impedance presented by the transformer of the diierentialsystem 2'1 for-the low-frequencysignal currents, and to thelow impedance presented by the condenser 3l (shunting the circuit' ofv the signalling device)v for the telephone talkingA currents. The connections of the circuitsl of' the' talking current repeater and of the signalling arrangement for the oppositev direction 9*-l0are symmetrical with those corresponding' tothe direction-V Iii-4),A and will not be described. l

Itis evident that' the described arrangement of Fig. 6V cannot work in entirelyV satisfactory manner as far as the iiltering is concerned-that is', the suppression of the mutual influence of the talking current repeater, and of the signalling arrangement, owing'to the widedierence of irequency usually provided between the telephone talking'currents andthe signalling currents. In theucase in which itshould be desired to-produce. asystem with a reduced diierencebetweenthese frequencies, it would benecessary` to connecttrue ltersl between the. various. circuits..

The. signallingarrangementto. which this presis ent invention relates oiers the advantage of. onlyl using as activemembers, vacuum. amplier: tubes such. as.: triode,. pentode and: so on, the perfect fidelity; of. which is known, to the exclusion` of; ani! electromechanical' device or gas discharge tubeL Theretransmission oie the signals..may; therefore be practicallirl linear.. is: particularly* important in tha case wlricniit; is; desired; totV transmit; rapid andi. relatively com plexi. signals. as: dialing currentsi. for example sig@ ria-ls; atcycles. per' second intr-airis; ot 66 imille seconds and with intervals ofv 32' milliseconds; employed in the: practice of automatic: telephony..

The. use.l for the signalling; arrangementfot the.'V tubes of the repeater' with. which! itis-associated@ allowsv of especially.' advantageousv embodiments: having. relatively. small; overall dimensions;

Having: now. particularly described and ascen-I tained the .nature ofil my said invention andi in f what manner the: same-l is.v torbe performed.. 1I:-

declare that'whatil' claim-is: f

1; In a two-way' repeater tortel'ephcne lines; a first pair of line terminals, a second pair: off-f line terminals, afirstchannel fortransmitti'ng.Y signals from said. first.; terminalsY tosaid second terminals; a, secondichannely for transmitting siglenal'sfromsaid? secondi terminals.- to said first. terri mina-ls, a first; tubel amplifier comprised'. said"1 firstY channel and! having its input4 connected; therein-in. thedirection of sa-id'rstA terminals; a' second' tube amplier comprised in. saidfsecond-j channel and?` having itsinput v connected"-V thereint in the f direction off' said' secondil terminals,A aiA i'st locking rectifier unit having its inputI comfiected4` tol` said irstchannel-'and having its. output. con-- nected .and poled to f applyf negative" bias'rt'of thegridcff' said secondi tube amplifier when signal output is applied tosaid first terminals,v a second` locking rectiii'er-l unit having itsf inputI connected tosai-'d secondY channel and having itsioutputf con-- nected and pol'ed toA apply negative bias to they grid'-v of said/first tube amplifier whensignai= output is. applied, toi said second termina-ls; afl-rst liminalcontrol short-cirouitingf device inserted'- in' a-said channel' in thepathof' current -ifronr said' first .terminals-to the inputA of"A saidfsecondl ampli er 'at-a point of said -pathwhich-v is' beyond'"tlfie'v point otconnecting the input ot'said ii-rst lockingdevi'ceto said first channel on the sideltowardlv saids second line terminals.l said-nist' liminal conof said rst amplifier at a pointof*saictjpath-A Whiclfris-'beyond the pointv of: connecting the'input offsaid second'locking device to said second-chan nei orirtheV sidetoward said first line terminals:

2.I In a'two-way repeater for-telephone*linesfa. rst' pair' of' line-terminals a secorid'-r pair off-line terminals, afirst channelfor transmitting signals from saidfrst terminals to said second terminals; a second channele for vtransmitting signals v from" said.v secondy terminals to said 'rst'I terminals; a

vfirst tubeiampliercomprisedin said rst'cha'nnel and having'its input connectedtolsaid first tenmi-nals, a ii'rstliminal' control `shortcircuiting device connected between the output of'fsaiii'i'rstrv ampli'er and; said second terminals`I andbeing so. constructed. that under an` applied output signal frome said rstl'airip'lier-v` below a deter-- mined-limina-lf valueabut not abovethat liminal; value. it; constitutes. substantiallya: short circuit acrossgth'e outputoot said firstzamplifien: a second-21 tube. ampliiier.A comprisedrinsaid second chanr'i'eiT advantagai` and having its input connected to said second terminals, a second liminal control device constructed'similarly to said first liminal control device and connected between the output of said second amplifier and said first terminals, a first locking rectifier unit having its input connected to saidfirst channel at a point between the output of said first amplifier and said first liminal control device and having its output connected and poled to apply negative bias to the grid of said second tube amplifier when signal output is delivered by said first amplifier, and a second locking rectifier unit having its input connected to said second channel at a point between the output of said second amplifier and said second liminal control device and having its output connected and poled to apply negative bias to the grid of said first tube amplifier when signal output is delivered by said second amplier.

3. In a two-way repeater for telephone lines, a first pair of line terminals, a second pair of line terminals, a first channel for transmitting signals from said first terminals to said second terminals, a second channel for transmitting signals from said second terminals to said first terminals, a first tube amplifier comprised in said first channel and having its input connected therein in the direction of said first terminals, a second tube amplifier comprised in said second channel and having its input connected therein in the direction of said second terminals, a first locking rectifier unit having its input connected to said first channel at a point thereof on the output side of said first amplifier, and having its output connected and poled to apply negative bias to the grid of said second tube amplifier when signal output is delivered by said first amplifier, a second locking rectifier unit having its input connected to said second channel at a point thereof on the output side of said second amplifier and having its output connected and poled to apply negative bias to the grid of said first tube amplifier when signal output is delivered by said second amplifier, a first liminal control short-circuiting device connected between said second terminals and the input of said second amplifier and ybeing so constructed that under an applied input signal thereto below a determined liminal value but not above that liminal value said first liminal control device constitutes substantially a short circuit across said second channel, and a second liminal control device constructed similarly to said first liminal control device connected between said first terminals and the input of said first amplifier. Y

4. A repeater according to claim 2, each said liminal control device comprising a pair of opposing principal rectiiier elements connected in series across its said channel and a source of biasing voltage connected to the common point of said principal rectifier elements, and further comprising two pairs of auxiliary rectifier elements connected in parallel and each pair of said auxiliary rectifier elements being respectively inserted in series in the respective sides of its channel, said elements of each said pair of said auxiliary rectifier elements being oppositely poled.

V5. In a two-Way repeater for telephone lines, a first pair of line terminals, a second pair of line terminals, first and second selective filtering input means connected to each said pair of terminais and adapted to separate talking currents applied to said pair of terminals from signaling currents applied thereto, and having input con- 8 nections and signaling output connections and talking output connections, a first signaling channel for transmitting signal currents from the signaling output connections of said first input means to said second pair of terminals, a second channel for transmitting signal currents from the signaling output connections of said second input means to said first pair of terminals, a first tube amplier having connected in series in its input circuit the signaling output connections and the talking output connections of said first input means, first output selecting means comprising said second input means connected in series in the output circuit of said first amplifier and connected to said first signaling channel and adapted to deliver amplified talking output current and amplified signaling current from the output of said first amplifier to said second pair of terminals, a second tube amplifier having connected in series in its input circuit the signaling output connections and the talking output connections of said second input means, the output circuits of said two amplifiers respectively being comprised in said first and second signaling channels, second output selective means comprising said first input means connected in series in the output circuit of said second amplier and connected to said second signaling channel and Y adapted to deliver amplified talking current and amplied signaling current from the output of said second amplifier to said first pair of termi-1 nais, a first locking rectifier unit having its input connected to the output circuit of said first amplifier and having its output connected and poled to apply negative bias to the grid of said second amplifier when signal output is delivered by said first amplifier, a second locking rectifier unit having its input connected to the output circuit of said second amplifier and having its output connected and poled to apply negative bias to the grid of said first amplifier when signal output is delivered by said second amplifier, a first liminal control short-circuiting device inserted insaid first signaling channel between said second pair of terminals and the point Where the input connections of said first locking rectifier unit are connected to the output circuit of said first amplifier, and being so constructed that under an applied input signal applied from said first amplifier below a determined liminal value but not above that liminal value the said first laminal control unit constitutes substantially a short circuit across said first signaling channel, and a second liminal control short-circuiting device constructed similarly to said first liminal control' device and inserted in said second signaling channel between said first pair of terminals and the point where the input connections of said second locking rectifier unit are connected to the output circuit of said second amplifier.

6. A repeater according to claim 5, each said liminal device comprising a pair of opposing principal rectifier elements connected in series across its said channel and a source of biasing voltage connected to the common point of said principal rectifier elements, and further comprising two pairs of auxiliary rectifier elements connected in parallel and each pair of said auxiliary rectifier elements being respectively inserted in series in the respective sides of its channel, said elements of each said pair of said auxiliary rectifier elements being oppositely poled.

v'7. In a two-way repeater for telephone lines. a first pair of line terminals, a second pair-0f line terminals, a first channel for transmitting signals from said Iirst terminals to said second terminals, a second channel for transmitting signals from said second terminals to said first terminals, a rst tube amplifier comprised in said rst channel and having its input connected to said rst terminals, a first liminal control shortcircuiting device connected between the output of said iirst amplier and said second terminals and being so constructed that under an applied output signal from said rst amplifier below a determined liminal value it constitutes substantially a short circuit across the output of said first amplier and also constitutes a high resistance in series between said output of said rst amplifier and said second terminals, and under an applied output signal from said first amplifier above said determined liminal value it constitutes a shunt of high resistance across the output of said iirst amplifier and a resistance of negligible value in series between said output of said first amplifier and said second terminals, a second tube amplifier comprised in said second channel and having its input connected to said second terminals, a second liminal control device constructed similarly to said first liminal control device and connected between the output of said second amplifier and said first terminals, a rst locking rectifier unit having its input connected to said first channel at a point between the output of said iirst amplifier and said first liminal control device and having its output connected and poled to apply negative bias to the grid of said second tube amplier when signal output is delivered by said first amplier, and a second locking rectifier unit having its input connected to said second channel at a point between the output of said second amplifier and 10 said second liminal control device and having its output connected and poled to apply negative bias to the grid of said iirst amplifier when signal output is delivered by said second amplifier.

8. A repeater according to claim 7, each said liminal control device comprising a pair of opposing principal rectier elements connected in series across its said channel and a source of biasing voltage connected to the common point of said principal rectifier elements, and further comprising two pairs of auxiliary rectier elements connected in parallel and each pair of said auxiliary rectier elements being respectively inserted in series in the respective sides of its channel, said elements of each said pair of said auxiliary rectifier elements being oppositely poled. D

HENRI GARDRE.

REFERENCES CETED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 1,795,295 Dahms Mar. 10, 1931 1,811,947 Legg June 30, 1931 1,811,963 Peterson June 30, 1931 1,866,592 Bjornson July 12, 1932 2,018,464 Nebel Oct. 22, 1935 2,019,577 Mitchell et al. Nov. 5, 1935 2,422,309 McCreary June 17, 1947 FOREIGN PATENTS Number Country Date 287,651 Italy July 31, 1931 643,015 Germany Mar. 31, 1937 

